Baby sleep patterns: An evidence-based guide

Baby sleep patterns vary from infant to infant, and they
change over time. So there is no one,
universal chart or instruction manual that can predict when and how your baby
will sleep.

But scientific research can help us understand the range of
variation, and the general trends.

Here I provide a timeline of quick facts, followed by a longer article that will help you understand what can speed up -- or slow down -- the development of baby sleep patterns.

I'll also help answer questions like "how much sleep does a baby need?" and "when do babies start sleeping through the night?"

A developmental timeline of baby sleep patterns

0-3 months. Newborns sleep in short bouts scattered throughout the 24-hour day. As the days pass, they gradually develop a tendency to sleep more at night.

Total sleep duration varies; about half of all infants get between 13 and 16 hours of sleep every 24 hours.

Overall, their sleep is light and restless. Unlike older children and adults, young babies usually lapse into REM, or rapid eye movement sleep, immediately after dozing off, and they spend a lot more sleep time in REM than we do.

They move around a lot, and sometimes even vocalize. Read more about newborn baby sleep patterns here.

In addition, babies are more likely to sleep for extended
periods at night.

For example, in one study, approximately 50% of parents reported infant sleep bouts lasting 5 hours or more (Henderson et al 2010).

But multiple
daytime naps are still common, and there is still a lot of individual variation.
For most babies this age, total sleep duration is likely in the range of 12-16
hours.

5-6 months. Around this age, most parents report that their babies are sleeping without
interruption at night for 5 hours or more, and many claim their babies sleep
for more than 10 hours at night (Mindell et al 2016; Iglowstein; Jiang et al
2007).

Nevertheless, it's not unusual for parents to report that their babies awaken
at least once during the night, and some babies don't settle into 5+ hour sleep bouts until they are considerably older (see below).

Babies typically take several naps during
the day, and average total sleep duration remains in the range of 12-16 hours.

7-12 months. If your baby still isn't sleeping for at least 5 hours at a stretch, you're in good company. In one study of American infants, more than 15% of parents reported that their 12 month old babies hadn't yet reached this milestone (Henderson et al 2010).

But for most families, nights have quieted down. It isn't that these babies don't experience night wakings. On the contrary, it's normal for infants this age to awaken 3-4 times each night. But many babies have learned to fall back to sleep quietly on their
own, so that their parents aren't even aware that their infants had awakened (Goodlin-Jones et al 2001; Dias et al 2018).

By the end of the first year, babies tend to spend less time napping. But naps appear to remain helpful, and babies typically take one or two each day. Most babies continue to get sleep approximately 12-16 hours every 24 hours.

Factors that affect the timeline -- or temporarily shake things up

Baby sleep patterns are shaped by a mix of genetic and environmental factors. For instance, in two studies of 6-month old babies, almost half the individual variation in nighttime sleep duration could be explained by genetic factors (Dionne et al 2015; Touchette et al 2013).

By contrast, individual differences in the trajectory of napping -- whether babies decreased napping from 6 months onward -- were almost entirely explained by environmental factors, like whether parents promote or discourage napping.

How do genes influence baby sleep patterns? One route is by shaping infant temperament. If your baby tends to be less adaptable and more irritable, it's going to be harder to quiet him or her down, and studies confirm that such babies sleep less overall (Weissbluth and Liu 1983; Van Tassel 1985; Scher et al 1992; Sadeh et al 1994; Scher et al 1998).

It's also likely that some babies need less sleep than others, and that specific aspects of sleep -- like how easily an infant is awakened -- are shaped by genes.

But it's clear that parents can affect baby sleep patterns. We've already noted the effects parents have on napping. In addition, parents can influence the development of circadian rhythms, and help babies learn to resettle themselves after waking at night (see below).

Finally, it appears that baby sleep patterns vary from one country to the next. For example, studies suggest that babies in Japan and Italy tend to sleep less than their counterparts in Switzerland and Canada (Kohyama et al 2011;
Bruni et al 2014; Iglostein et al 2003; Mindell et al 2010).

And motor milestones -- like learning to crawl, learning to stand, and learning to walk -- tend to disrupt baby sleep patterns (Atun-Einy Scher 2016; Scher and Cohen 2015). If your baby is mastering a new physical skill, you might observe temporary changes.

Digging deeper: What makes baby sleep patterns different from our own, and how can we help babies develop more mature sleep habits?

The foregoing summary offers some quick answers. But it pays to learn more about baby sleep patterns. It can help you avoid mistakes, and support the development of more mature sleep rhythms.

Circadian rhythms: How long does it take for babies to
synchronize with the natural, 24-hour day?

Young babies are notorious for sleeping and waking at
awkward times. In part, this is because their circadian rhythms -- recurring,
24-hour cycles of physiological activity -- aren't synchronized with the
natural rhythms of daylight and darkness.

You may have heard that it takes 3-4 months for babies to
develop mature circadian rhythms. But research confirms that the timing varies,
and that babies synchronize sooner when we provide them with the right
environmental cues.

Light has the biggest
impact on your baby's "inner clock,"so use it wisely.

In addition, involve
your baby in your daily activities, and avoid the temptation to turn nighttime
feedings into social events.

When you attend to your baby in the middle of
the night, be soothing, but avoid engaging your baby with eye contact and
conversation. Keep the lights off, and your behavior low key.

Sleep stages and sleep cycles: How do baby sleep patterns unfold over
the course of the night, and when are infants most likely to awaken?

To answer this, it helps to review what adult sleep is like.

For us, sleep isn't a single continuous state of coma-like unconsciousness. We pass through a series of sleep stages, beginning with light sleep, progressing to deep sleep, and ending with rapid eye movement sleep, or REM -- the sleep stage associated with busy brain activity, dreaming, and the loss of muscle tone.

We don't move around during REM unless we suffer from certain sleep disorders.

The whole sequence takes approximately 90-100 minutes, after which we either awaken or repeat the cycle. Sleep lab research shows that we're especially prone to awaken during or immediately after REM (Akerstedt et al 2002).

But throughout each sleep cycle, we also experience multiple arousals -- brief, partial awakenings.

These are a normal part of sleep, fleeting "check ins" that help the brain keep tabs on potential threats. If there is nothing to attract our interest or concern, the arousal process is aborted, and the brain goes back to sleep.

For infants, things are much the same.

Babies experience distinct sleep stages, including an infant version of REM, called "active sleep."

They also experience many brief arousals during the night, fleeting moments of drowsy wakefulness that you might not even notice.

And these arousals are especially common during the baby equivalent of REM, sometimes called "active sleep" (Grigg-Damberger et al 2007; Montemitro et al 2008).

But baby sleep patterns differ in crucial ways.

Baby sleep cycles are shorter -- on average, about 50-60 minutes long (Jenni and Carskadon 2000; Jenni et al 2004; Grigg-Damberger 2017). And for the youngest babies -- those under 3 months of age -- the average sleep cycle looks like this:

Active sleep (REM)

Transitional sleep

Quiet sleep

That is, babies begin a sleep bout in REM, next switch into a sleep stage called transitional sleep, and then finally arrive at a sleep stage called "quiet sleep" (Parslow et al 2003).

Another difference is that babies spend a lot more time in REM than we do.

Whereas average adult spends only 20% of total sleep time in REM, for newborns the percentage is higher than 50% (Grigg-Damberger 2017). Time spent in REM declines as babies get older, but the change my come slowly. For some 9-month-old babies, REM still makes up 50% of their total sleep hours (Montemitro et al 2008).

But perhaps the most consequential difference for new parents is that baby sleep patterns can deceive us. During REM and transitional sleep, babies can sometimes appear to be awake.

As noted, we adults don't move around during REM. We
experience sleep paralysis. But for young babies -- especially babies under the
age of 3 months -- this isn't the case. They usually retain muscle tone, and
they use it. A lot.

They twitch, wiggle, stretch, and thrash. They may frown or
smile, or launch into a burst of sucking movements. They may vocalize too (Grigg-Damberger
2017; Barbeau and Weiss 2017).

So babies in REM may appear deceptively awake, and the same
can be said for babies in transitional sleep. During transitional sleep,
newborns become more likely to vocalize, and sometimes even open their eyes
(Barbeau and Weiss 2017).

It's really only during "quiet sleep" that young
babies present us with reliable cues that they are asleep: Aside from the
occasional sigh, their breathing becomes slow and regular, and they scarcely move
at all. But young babies spend only a minority of their time in quiet sleep --
approximately 20 minutes per sleep cycle (Grigg-Damberger 2017).

This can lead the exhausted parent to make an
understandable but unfortunate mistake: You misread your baby's cues, and end
up disrupting your infant's sleep.

It happens innocently enough.

You hear your baby whimper. You
observe movement. You might even see that your baby's eyes are open. So you bow
to the inevitable, and swoop in to soothe him or her.

You start talking, or you
pick your baby up.

It seems like a good idea at the time. Isn't it better to be
proactive, to jump in before your baby has become really noisy or agitated?

But your basic premise was faulty. Your baby wasn't awake,
but rather in REM or transitional sleep. Or perhaps what you mistook for waking
was one of those brief arousals -- a
fleeting moment of drowsy wakefulness that would quickly transitioned back into
sleep if you'd left your baby alone.

Either way, you've intervened unnecessarily, and added a
night waking to the schedule that might not otherwise have happened. And you
may have denied your baby the experience of falling back to sleep on his or her
own, without any fuss or distress.

If you make this mistake regularly, you may be teaching your baby to turn brief
arousals into full-blown waking sessions -- and to expect lots of interaction
with you.

To avoid this, be patient and observant before responding to
your baby at night.

Get to know your baby's quirks. And be aware that your
social cues -- especially the sound of your voice -- can have particular
powerful effect. Babies can awaken quickly when they hear us talk.

In fact,
researchers note that babies "arouse more easily in response to their
mother's voice than to a smoke alarm" (Grigg-Damberger et al 2007).

Why do babies spend so much time sleeping light?

It might seem like Mother Nature made a terrible mistake.
Wouldn't it be better if our babies slept soundly and deeply all night? But REM
may be important for a baby's brain development (Siegel 2005). According to one
theory, it could be a time for the brain to test its wiring -- including the
nerves that run to the skeletal muscles.

So there is a crucial survival advantage to sleeping light,
and that's what REM sleep delivers.

Researchers have demonstrated this in experiments on sleeping infants. They subjected the babies to mild reductions in oxygen. Would the infants promptly awaken?

Babies did arouse quickly -- if they had been in REM sleep. But if the oxygen levels dropped while babies were in quiet sleep, the outcome was different. Babies aroused more slowly, or failed to awaken altogether (Parslow et al 2003; Richardson et al 2007).

It appears, then, that long bouts of quiet sleep could be hazardous, at least for infants young enough to be at risk for
SIDS. For the first 6 months, sleeping relatively light -- and being easily
aroused -- is a good thing. It makes babies safer.

As a result, we must be thoughtful when we're evaluating
sleep advice. A given tactic isn't automatically desirable because it results
in babies sleeping more deeply or for longer stretches of time.

On the
contrary, experts recommend some practices because they support more frequent
arousals in young infants.

For example, babies who are breastfed tend to experience
more frequent arousals than babies who are formula-fed. Researchers suspect
this is one reason why breastfed infants have lower rates of SIDS (Horne et al
2004b; Franco et al 2000).

You can read more about environmental risk factors for SIDS -- and sleep practices to avoid -- here.

So how much sleep do babies need?

This is a surprisingly difficult question to answer,
especially for younger babies.

We know what international surveys tell us about typical baby
sleep patterns. Among parents with babies under the age of 3 months, approximately 50% say their infants sleep between 13-16 hours over the course of a 24 hour day (Iglowstein et al 2003; Bruni; Netsi et
al 2017; Kohyama et al 2011).

This might suggest that 13-16 hours is what most young babies need. But the surveys have limitations.

First, they are based on parental reports, which can be inaccurate. When scientists measure sleep objectively, they find disparities between parental perceptions and reality. Parents tend to overestimate total sleep duration, and underestimate the frequency of night wakings (Goodlin-Jones et al 2001; Galland et al 2016).

Second, even if we could be certain about the numbers, the numbers wouldn't constitute proof about what babies need. Maybe the babies in these surveys aren't getting enough sleep. Or maybe they're getting too much.

What's needed is research that addresses the health consequences of sleep, and unfortunately such research is in short supply (Paruthi et al 2016).

Citing this lack of evidence, the American Academy of Sleep Medicine has declined to issue any specific recommendations about sleep duration for babies under the age of 4 months (Paruthi et al 2016).

For older babies (4-12 months), the Academy notes that some studies have found links between emotional or behavioral problems and short sleep. On this basis, the Academy advises that 4- to 12-month-old
babies are at a lower risk for problems if they get between 12-16 hours of
sleep every 24 hours (Paruthi et al 2016).

What about sleeping through the night? When do babies begin
sleeping in long, uninterrupted nighttime bouts?

Understandably, parents want their babies to "sleep
through the night." But, as we've already noted, nobody truly sleeps
through the night -- not in the sense of remaining in a constant sleep state
for hours on end.

Researchers have captured this in video
recordings: Babies under the age of 12 months awaken, on average, 3-4 times a
night (Goodlin-Jones et al 2001).

So it isn't realistic to expect your baby to stop awakening
at night. Nor would that be a good idea. As we've seen, arousals serve an important function.

Instead, a more reasonable goal is for your baby to settle down at night for at least 5 hours at a stretch. When your baby experiences an arousal, he or she quickly falls back to sleep -- without your assistance.

That's what's really going on when parents say their babies
sleep for long periods of time. The infants are
experiencing normal arousals and night wakings, but their parents aren't aware of these interruptions. Babies are staying quiet, and returning to sleep on their own.

So when does this happen? At what age do babies keep quiet
for at least 5 hours? Between, say, midnight and 5am?

The answer is that it varies.

Some babies achieve this
milestone at two months postpartum. But most babies don't get there until 4-6
months, or even later.

We can see this pattern in a study that tracked 75 American
infants over time. Jacqueline Henderson and her colleagues asked their parents
to keep sleep diaries -- 6 days per month -- throughout the first 12 months
postpartum.

Most parents didn't record long stretches of sleep, not when
their babies were very young. At two months, only 8% of parents reported that their
babies were sleeping uninterrupted between the hours of midnight and 5am.

But by 4 months, approximately 50% of parents made this
claim. And by 5-6 months, the majority of parents -- about 70% -- said their
babies were sleeping without any perceived interruptions during these potentially
crucial hours. At 12 months, the percentage had increased to 84% (Henderson et
al 2010).

But what if your baby isn't a "good sleeper"? Is
there something you can do to improve baby sleep patterns?

We've already seen that you can help your baby develop
mature circadian rhythms.

If your baby isn't sleeping well at night, make sure
your baby is getting the right environmental cues -- bright light during the
day, darkness before bedtime, and a boring, peaceful nighttime atmosphere. This
will help your baby get sleepy at the right time -- and spend more time
sleeping at night.

We've also seen that there are mistakes parents can make
during the night -- mistakes that can prevent babies from learning to fall back
to sleep on their own.

If you can resist the urge to interact with a baby who seems
to be waking -- and wait to make sure the baby isn't really asleep, or about to
go back to sleep without your assistance -- you'll help your baby learn to
sleep for longer periods.

Whether your baby shares a room with you, or sleeps
elsewhere, you can make it a point reassure and calm your baby before bedtime.
Being sensitive and responsive to your baby's moods is called "emotional
availability," and studies show that it has an important impact on the way
infants sleep. When parents show emotional availability at bedtime, babies wind
down more easily, and they experience fewer sleep problems (Teti et al 2010; Jian and Teti 2015).

2. If you baby doesn't
seem to be sleepy at bedtime, don't try to force it.

Getting pushy doesn't make babies any sleepier. If anything,
it makes them more excitable. And you don't want your baby to associate bedtime
with conflict. That can be a difficult lesson to unlearn!

So instead, try the technique known as "positive
routines and faded bedtime," which you can read about here. It's a method for resetting your infant's inner clock, and overcoming bedtime resistance.

It's not clear if excessive, inconsolable crying disrupts baby sleep patterns, but it definitely stresses out parents. And when parents are stressed out, they suffer more sleep problems. Read more about inconsolable crying and its possible causes here.

4. Watch out for
those late naps.

Naps are good for babies, but poorly-timed naps can cause trouble. A long snooze in the late afternoon can delay drowsiness for hours, wrecking havoc with your baby's bedtime.

References: Baby sleep patterns

For a complete list of the studies and publications cited in this article,
click here.